IMDMAN

So I'm new to the gas boat thing and am wondering if you guys can give some general setup instructions to make a boat go its best speed and still handle good. I know there are alot of things you can change so what are the secrets. I'm running a stock BJ55.</p>

Jon DesJardins

Just start with everything at neutral in relation to prop angle, trim tabs & rudders.
Then adjust one thing at a time to see how you like the changes.

gtopillado

Good advice above [sm=thumbup.gif] Set strut at 3/8 above sponsons and slowly go up from there.

dicko

There is a whole thread designated to getting the BJ55 going fast on here. Have a read through it & see what those guys did.

danielplace

Not really wanting to discourage your plans for more speed on the BJ55 but quite honestly they are already running at the speeds that hull was designed to be run at and doing mods will certainly make it go faster but it also magnifies
it's handling shortcomings. No matter what you try they will never be a stable and fast boat and will only find yourself upside down more often besides that the hulls strength will be tested beyond it's limit and not always have a happy ending. To be perfectly honest. Run the BJ get some wheel time and play with props and adjustments and learn what you can from it then move on to a hull designed to go fast. I modded one almost as far as you would want and it was less enjoyable than stock. Fast yes, upside down always. It is just impossible not to use the throttle if it's there. Just trying to save you some money, time and stress not bad mouthing your boat or what you would like to do with it. The only way most will believe that is the first day they buy or drive a hull designed to go fast. Most RTR's were designed to do the speeds they do with a stock engine by having lift built into the hull and when you add more power they usually have issues.

IMDMAN

thanks for the replys. I'm not really wanting t o mod my boat, just looking for the tricks of fine tuning a machine.
When you talk about adjusting the prop 3/8 of an inch above the sponsons, do you mean the bottom of the boat?

martno1fan

The sponsons are what the boat rides on so measure up from there with it sat on a flat table .
Mart

PEERPSI

Yep, set the boat on a table top and measure the gap between the ferrule on the prob shaft where it meets the flex shaft coming out of the stuffing tube. The propellers used on these models are intended to run at about 30% of the blade radius submerged. The stock propeller from Proboat is a 270 2.74 diameter with 4.2 inches of pitch. In metric sizing that would be a 7015/2, the 2 meaning 2 blade. So somewhere between .2259 inches and .3637, allowing for a 3/8" shaft diameter at the prop shaft ferrule, will give you 35-30% of the prop radius in the water. You also want to concern yourself with strut angle. Negative tilt, meaning the propeller center is lower then the prop shaft where it meets the stuffing tube, will want to pull the bow down. Positive, prop center higher then the prop shaft where it meets the stuffing tube, lifts the bow up and pushes the transom down. Ideally you would run neutral as this would be your most efficient setting. However, conditions will dictate what you need. Personally I set it at about a half degree negative to help prevent blow overs.

I have a spreadsheet that I use to help calculate strut depth and efficency based on RPM and actual speed measured. Anyone that wants a copy is welcome to it.

PEERPSI

http://www.ppbracing.com/technical_t...adjustment.htm

A picture is worth a thousand words!

Jon DesJardins

perfect display with directions

IMDMAN

thanks alot guys, these are the kinds of things we all need to know. Without having the basic understanding we will go in circles and get nowhere. This kind of info should be in a sticky.